Question

I’ve got a nested foreach loop that I really need to cut the computation time on. Each collection is at about 50 members, so the extrapolation is huge. I’ve looked at a lot of information about SelectMany, but I’m still not entirely sure how to use it, or if it’s the correct solution.

List<string> StringList; //Populated in previous code
Type[] assemblyTypes = RandomAssembly.GetTypes();

foreach (String name in StringList)
{                               
  foreach (Type at in assemblyTypes)
  {                             
    if (name == at.Name)
    {                                       
      //Do stuff.
    }
  }
}

Thanks in advance!

Answer 1

Use a lookup (such as a dictionary) to increase the speed of checking for a type name:

List<string> StringList; //Populated in previous code
Dictionary<string,Type> assemblyTypes = RandomAssembly.GetTypes()
    .ToDictionary(t => t.Name, t => t);

foreach (String name in StringList)
{                               
    if (assemblyTypes.ContainsKey(name))
    {                                       
      //Do stuff.
    }
  }
}

You should also check which of the 2 collections (StringList or assemblyTypes) is likely to be larger. You generally want the larger one to be converted to the lookup in order to reduce the number of iterations.